#include<iostream>
#include<vector>
#include<queue>
using namespace std;
int main()
{
  int h,w;
  cin >> h >> w;
  vector<vector<int>>num(h,vector<int>(w));
  for(int i=0;i<h;i++)for(int j=0;j<w;j++)cin >> num[i][j];
  priority_queue<vector<int>,vector<vector<int>>,greater<vector<int>>>prq1;
  priority_queue<vector<int>,vector<vector<int>>,greater<vector<int>>>prq2;
  vector<vector<int>>color(h,vector<int>(w,-1));
  prq1.push({0,0,0});
  prq2.push({0,h-1,w-1});
  int cnt=1,ans=0;
  while(true){
    ans++;
    if(cnt==1){
      int a,b;
      while(true){
	vector<int>hako=prq1.top();
	prq1.pop();
	a=hako[1];
	b=hako[2];
	if(color[a][b]==-1)break;
      }
      color[a][b]=1;
      if(a-1>=0){
	if(color[a-1][b]==0)break;
	else if(color[a-1][b]==-1)prq1.push({num[a-1][b],a-1,b});
      }
      if(b+1<w){
	if(color[a][b+1]==0)break;
	else if(color[a][b+1]==-1)prq1.push({num[a][b+1],a,b+1});
      }
      if(a+1<h){
	if(color[a+1][b]==0)break;
	else if(color[a+1][b]==-1)prq1.push({num[a+1][b],a+1,b});
      }
      if(b-1>=0){
	if(color[a][b-1]==0)break;
	else if(color[a][b-1]==-1)prq1.push({num[a][b-1],a,b-1});
      }
      cnt=0;
    }
    else{
      int a,b;
      while(true){
	vector<int>hako=prq2.top();
	prq2.pop();
	a=hako[1];
	b=hako[2];
	if(color[a][b]==-1)break;
      }
      color[a][b]=0;
      if(a-1>=0){
	if(color[a-1][b]==1)break;
	else if(color[a-1][b]==-1)prq2.push({num[a-1][b],a-1,b});
      }
      if(b+1<w){
	if(color[a][b+1]==1)break;
	else if(color[a][b+1]==-1)prq2.push({num[a][b+1],a,b+1});
      }
      if(a+1<h){
	if(color[a+1][b]==1)break;
	else if(color[a+1][b]==-1)prq2.push({num[a+1][b],a+1,b});
      }
      if(b-1>=0){
	if(color[a][b-1]==1)break;
	else if(color[a][b-1]==-1)prq2.push({num[a][b-1],a,b-1});
      }
      cnt=1;
    }
  }
  cout << ans-2 << endl;
}